Synthesis of CoC2O4·2H2O nanorods and their thermal decomposition to Co3O4 nanoparticles

A highly efficient process to enhance the bioleaching of spent lithium-ion batteries by bifunctional pyrite combined with elemental sulfur

Bioleaching technologies have been shown to be an environmentally friendly and economically beneficial tool for extracting metals from spent lithium-ion batteries (LIBs). However, conventional bioleaching methods have exhibited low efficiency in recovering metals from spent LIBs. Therefore, relied on the sustainability principle of using waste to treat waste, this study employed pyrite (FeS2) as an energy substance with reducing properties and investigated its effects in combination with elemental sulfur (S0) or FeSO4 on metals bioleaching from spent LIBs. Results demonstrated that the bioleaching efficiency was significantly higher in the leaching system constructed with FeS2 + S0, than in the FeS2 + FeSO4 or FeS2 system. When the pulp densities of FeS2, S0 and spent LIBs were 10 g L-1, 5 g L-1 and 10 g L-1, respectively, the leaching efficiency of Li, Ni, Co and Mn all reached 100%. Mechanistic analysis reveals that in the FeS2 + S0 system, the activity and acid-producing capabilities of iron-sulfur oxidizing bacteria were enhanced, promoting the generation of Fe (Ⅱ) and reducible sulfur compounds. Simultaneously, bio-acids were shown to disrupt the structure of the LIBs, thereby increasing the contact area between Fe (Ⅱ) and sulfur compounds containing high-valence metals. This effectively promoted the reduction of high-valence metals, thereby enhancing their leaching efficiency. Overall, the FeS2 + S0 bioleaching process constructed in this study, improved the leaching efficiency of LIBs while also effectively utilizing waste, providing technical support for the comprehensive and sustainable management of solid waste.

Removal of Pb ions using green Co3O4 nanoparticles: Simulation, modeling, adsorption, and biological studies

Chemical co-precipitation synthesized novel and green cobalt-oxide nanoparticles (Co₃O₄-NPs) utilizing cobalt nitrate as cobalt precursors. FTIR, Raman, scanning electron microscopy, UV visible, X-ray powder diffraction, and BET was used to analyze the surface characteristics, composition, and morphology, of the NPs. These green Co₃O₄-NPs were employed to remove Pb ions from simulated wastewater solutions at various pH, adsorbate, temperature, and dose concentrations. At dose 20 mg/L, pH 6.0, 20 mg/L (Pb(II) solution, 25 °C of temperature, and 45 min for equilibrium, nearly 99.44% of Pb ions were removed. To evaluate the kinetic data, four different kinetic equations were used. The data fit the Elovich rate equation better than the other three models. Thermodynamic and isothermal studies were also evaluated, and the maximum adsorption capacity of 450.45 mg/g was observed at 298.15 K. 0.1 M HNO_3, and 0.1 HCl were used to regenerate used Co₃O₄-NPs. Simulation results show the strong correlation of the Co atom in the Co₃O₄-NPs generates active delocalized surface states, which are energetically most favorable for heavy metal (Pb ions) adsorption and removal, supporting the experimental outcomes. In concluding remarks, green Co₃O₄-NPs can also be used as an adsorbent to remove Pb ions from wastewater bodies.

Synthesis, characterizations and electrochemical performances of anhydrous CoC2O4 nanorods for pseudocapacitive energy storage applications

To overcome the environmental challenges caused by utilization of fossil fuel based energy technologies and to utilize the full potential of renewable energy sources such as solar, wind and tidal, high power and high energy density containing large scale electrochemical energy storage devices are a matter of concern and a need of the hour. Pseudocapacitors with accessibility to multiple oxidation states for redox charge transfer can achieve a higher degree of energy storage density compared to electric double layer capacitors (EDLC) and the hybrid supercapacitor is one of the prominent electrochemical capacitors that can resolve the low energy density issues associated with EDLCs. Due to its open pore framework structure with superior structural stability and accessibility of Co2+/3+/4 redox states, porous anhydrous CoC2O4 nanorods are envisaged here as a potential energy storage electrode in a pseudo-capacitive mode. Superior specific capacitance equivalent to 2116 F g-1 at 1 A g-1 in the potential window of 0.3 V was observed for anhydrous CoC2O4 nanorods in aqueous 2 M KOH electrolyte. A predominant pseudo-capacitive mechanism seems to be operative behind the high charge storage at electrodes as intercalative (Inner) and surface (outer) charge storage contributions were found to be 75% and 25% respectively. Further, in full cell asymmetric supercapacitor (ASC) mode in which porous anhydrous CoC2O4 nanorods were used as positive electrodes and activated carbon (AC) was utilised as negative electrodes within an operating potential window of 1.3 V, a highest specific energy of W h kg-1 and specific power of ∼647 W kg-1 at 0.5 A g-1 current density were obtained with superior cycling stability. High cycling stability coupled with superior electrochemical storage properties make anhydrous CoC2O4 nanorods potential pseudo-capacitive electrodes for large scale energy storage applications.

Proton solvent-controllable synthesis of manganese oxalate anode material for lithium-ion batteries

Manganese oxalates with different structures and morphologies were prepared by the precipitation method in a mixture of dimethyl sulfoxide (DMSO) and proton solvents. The proton solvents play a key role in determining the structures and morphologies of manganese oxalate. Monoclinic MnC2O4·2H2O microrods are prepared in H2O-DMSO, while MnC2O4·H2O nanorods and nanosheets with low crystallinity are synthesized in ethylene glycol-DMSO and ethanol-DMSO, respectively. The corresponding dehydrated products are mesoporous MnC2O4 microrods, nanorods, and nanosheets, respectively. When used as anode material for Li-ion batteries, mesoporous MnC2O4 microrods, nanorods, and nanosheets deliver a capacity of 800, 838, and 548 mA h g-1 after 120 cycles at 8C, respectively. Even when charged/discharged at 20C, mesoporous MnC2O4 nanorods still provide a reversible capacity of 647 mA h g-1 after 600 cycles, exhibiting better rater performance and cycling stability. The electrochemical performance is greatly influenced by the synergistic effect of surface area, morphology, and size. Therefore, the mesoporous MnC2O4 nanorods are a promising anode material for Li-ion batteries due to their good cycle stability and rate performance.

A multi-technique approach to understanding delithiation damage in LiCoO2 thin films

We report on the delithiation of LiCoO₂ thin films using oxalic acid (C₂H₂O₄) with the goal of understanding the structural degradation of an insertion oxide associated with Li chemical extraction. Using a multi-technique approach that includes synchrotron radiation X-ray diffraction, scanning electron microscopy, micro Raman spectroscopy, photoelectron spectroscopy and conductive atomic force microscopy we reveal the balance between selective Li extraction and structural damage. We identify three different delithiation regimes, related to surface processes, bulk delithiation and damage generation. We find that only a fraction of the grains is affected by the delithiation process, which may create local inhomogeneities. However, the bulk delithiation regime is effective to delithiate the LCO film. All experimental evidence collected indicates that the delithiation process in this regime mimics the behavior of LCO upon electrochemical delithiation. We discard the formation of Co oxalate during the chemical extraction process. In conclusion, the chemical route to Li extraction provides additional opportunities to investigate delithiation while avoiding the complications associated with electrolyte breakdown and simplifying in-situ measurements.

CoC2O4·2H2O derived Co3O4 nanorods array: a high-efficiency 1D electrocatalyst for alkaline oxygen evolution reaction

Self-standing Co₃O₄ nanorods array on Co foil as a 1D OER catalyst electrode, only needs overpotential of 308 mV to drive 15 mA cm⁻² in 1.0 M KOH, with good long-term electrochemical durability and a high turnover frequency.

Solution-phase synthesis of transition metal oxide nanocrystals: Morphologies, formulae, and mechanisms

In this review, we provide a broad overview of solution-phase synthesis of transition metal oxide nanocrystals (NCs), including a substantial catalog of published methods, and a unifying classification and discussion. Prevalent subcategories of solution-phase synthesis are delineated and general features are summarized. The diverse morphologies achievable by solution-phase synthesis are defined and exemplified. This is followed by sequential consideration of the solution-phase synthesis of first-row transition metal oxides. The common oxides of Ti, V, Mn, Fe, Co, Ni, Cu, and Zn are introduced; major crystal lattices are presented and illustrated; representative examples are explained; and numerous synthesis formulae are tabulated. Following this presentation of experimental studies, we present an introduction to theories of NC nucleation and growth. Various models of NC nucleation and growth are addressed, and important concepts determining the growth and structure of colloidal NCs are explained. Overall, this review provides an entry into systematic understanding of solution-phase synthesis of nanocrystals, with a reasonably comprehensive survey of results for the important category of transition metal oxide NCs.

Development of PANI/MWCNTs decorated with cobalt oxide nanoparticles towards multiple electrochemical, photocatalytic and biomedical application sites

A facile synthesis of carbon nanotube hybrid nanostructures: energy and environmental applications.

Ligand-assisted soft-chemical synthesis of self-assembled different shaped mesoporous Co3O4: efficient visible light photocatalysts

Mesoporous self-assembled cobalt oxide (Co₃O₄) of different shapes was synthesized by a facile soft-chemical process using cobalt nitrate, oxalic acid and phosphoric acid in the presence of cationic templates, cetyltrimethylammonium bromide, 1-butyl-3-methylimidazolium bromide, and pyridinium bromide at 75 °C/2 h followed by calcination at 300 °C.

A facile synthetic approach for SiO2@Co3O4 core–shell nanorattles with enhanced peroxidase-like activity

SiO₂@Co₃O₄ core–shell nanorattles have been successfully synthesized through a novel self-template route by the calcination of SiO₂@α-Co(OH)₂ at 500 °C and the nanorattles exhibit enhanced peroxidase-like activity.

Direct Fabrication of Cobalt Oxide Nanoparticles Employing Sucrose as a Combustion Fuel

Combustion method has been used as a fast and facile method to prepare nanocrystalline Co3O4 spinel employing sucrose as a combustion fuel. The products were characterized by thermal analyses (TGA and DTA), X-ray diffraction technique (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) techniques. Experimental results revealed that the molar ratio of fuel/oxidizer (F/O) plays an important role in controlling the crystallite size of Co3O4 nanoparticles. Transmission electron microscopy indicated that the crystallite size of Co3O4 nanocrystals was in the range of 13–32 nm. X-ray diffraction confirmed the formation of CoO phase with spinel Co3O4. The effect of calcination temperature on crystallite size and morphology has been, also, discussed.

Morphology-controllable synthesis of cobalt oxalates and their conversion to mesoporous Co3O4 nanostructures for application in supercapacitors

In this work, one-dimensional and layered parallel folding of cobalt oxalate nanostructures have been selectively prepared by a one-step, template-free, water-controlled precipitation approach by simply altering the solvents used at ambient temperature and pressure. Encouragingly, the feeding order of solutions played an extraordinary role in the synthesis of nanorods and nanowires. After calcination in air, the as-prepared cobalt oxalate nanostructures were converted to mesoporous Co(3)O(4) nanostructures while their original frame structures were well maintained. The phase composition, morphology, and structure of the as-obtained products were studied in detail. Electrochemical properties of the Co(3)O(4) electrodes were carried out using cyclic voltammetry (CV) and galvanostatic charge-discharge measurements by a three-electrode system. The electrochemical experiments revealed that the layered parallel folding structure of mesoporous Co(3)O(4) exhibited higher capacitance compared to that of the nanorods and nanowires. A maximum specific capacitance of 202.5 F g (-1) has been obtained in 2 M KOH aqueous electrolyte at a current density of 1 A g(-1) with a voltage window from 0 to 0.40 V. Furthermore, the specific capacitance decay after 1000 continuous charge-discharge cycles was negligible, revealing the excellent stability of the electrode. These characteristics indicate that the mesoporous Co(3)O(4) nanostructures are promising electrode materials for supercapacitors.

Controlled synthesis of mesoporous hematite nanostructures and their application as electrochemical capacitor electrodes

In this work, iron oxalate (FeC₂O₄·2H₂O) with different morphologies was synthesized through a simple solution-based direct precipitation process. Three samples with distinct morphologies, i.e., microrods with a parallelogram-like cross-section, nanorods, and multi-layered nanosheets, could be obtained in a selective manner. We found that the shapes of the iron oxalate could be controlled just through simply altering the solvents used. The one-dimensional (1D) characteristic of the infinite linear chains and the selective interaction between solvents and various crystallographic planes of FeC₂O₄·2H₂O played an important role in the formation of FeC₂O₄·2H₂O with different morphologies. Phase-pure hematite (α-Fe₂O₃) had be obtained by annealing these as-prepared FeC₂O₄·2H₂O precursors without significant alterations in morphology. The as-obtained mesoporous α-Fe₂O₃ products had high specific surface areas with narrow pore size distribution. The electrochemical properties of the α-Fe₂O₃ electrodes were investigated using cyclic voltammetry (CV) and galvanostatic charge-discharge measurements by a three electrode system. The electrochemical experiments revealed that they showed a structure-dependence in their specific capacitances. The mesoporous multi-layered nanosheets exhibited a significant structurally induced enhancement of capacity properties associated with their novel structure characteristic in addition to the high specific surface area. They can present the highest specific capacitance value (116.25 F g⁻¹) and excellent long cycle life within the voltage window from - 0.6 to 0 V. This method can be easily controlled and is expected to be extended to produce other functional materials with controlled structure.